全文获取类型
收费全文 | 470200篇 |
免费 | 7426篇 |
国内免费 | 1674篇 |
专业分类
电工技术 | 8640篇 |
综合类 | 517篇 |
化学工业 | 68893篇 |
金属工艺 | 17035篇 |
机械仪表 | 14427篇 |
建筑科学 | 11956篇 |
矿业工程 | 1558篇 |
能源动力 | 12704篇 |
轻工业 | 46439篇 |
水利工程 | 4288篇 |
石油天然气 | 5609篇 |
武器工业 | 73篇 |
无线电 | 61192篇 |
一般工业技术 | 87885篇 |
冶金工业 | 86719篇 |
原子能技术 | 8023篇 |
自动化技术 | 43342篇 |
出版年
2021年 | 3654篇 |
2020年 | 2793篇 |
2019年 | 3520篇 |
2018年 | 5750篇 |
2017年 | 5817篇 |
2016年 | 6291篇 |
2015年 | 4237篇 |
2014年 | 7214篇 |
2013年 | 21806篇 |
2012年 | 12299篇 |
2011年 | 17058篇 |
2010年 | 13399篇 |
2009年 | 15036篇 |
2008年 | 16075篇 |
2007年 | 16041篇 |
2006年 | 14577篇 |
2005年 | 13194篇 |
2004年 | 12788篇 |
2003年 | 12475篇 |
2002年 | 11833篇 |
2001年 | 12107篇 |
2000年 | 11185篇 |
1999年 | 11851篇 |
1998年 | 27952篇 |
1997年 | 19823篇 |
1996年 | 15279篇 |
1995年 | 11793篇 |
1994年 | 10414篇 |
1993年 | 10198篇 |
1992年 | 7738篇 |
1991年 | 7271篇 |
1990年 | 6931篇 |
1989年 | 6505篇 |
1988年 | 6305篇 |
1987年 | 5366篇 |
1986年 | 5118篇 |
1985年 | 6241篇 |
1984年 | 5675篇 |
1983年 | 5164篇 |
1982年 | 4821篇 |
1981年 | 4940篇 |
1980年 | 4604篇 |
1979年 | 4352篇 |
1978年 | 4061篇 |
1977年 | 4802篇 |
1976年 | 5932篇 |
1975年 | 3640篇 |
1974年 | 3520篇 |
1973年 | 3589篇 |
1972年 | 2789篇 |
排序方式: 共有10000条查询结果,搜索用时 906 毫秒
151.
Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studies (UV–vis) are performed in corrosion‐promoting conditions (pH, NaCl), and detection studies by immersion in media associated with corrosion activity while microspheres' sensing activity is evaluated visually. Electrochemical characterization of AA2024 substrates in the presence of chitosan spheres is performed to understand material performance, and a color change is observed as a result of local pH increase in cathodic areas when corrosion takes place. These findings can be correlated with the results from release studies and seem a promising approach for corrosion sensing purposes, not only because pH increase is possible to detect due to corrosion, but also because chitosan is considered an environmentally friendly material. 相似文献
152.
Arif Karademir Cem Aydemir Semiha Yenidogan Emine Arman Kandırmaz Rukiye G. Kıter 《Color research and application》2020,45(6):1170-1178
Alkyd resins are generally used in the production of printing inks. All industries look for alternative raw materials in the production of ink with the growing inclination toward using natural products. Resins forming the vehicle of the ink to be obtained from natural resources will provide benefits for the environment, nature, and living creatures. The aim of the study was to promote the use of natural resin in the ink system. Natural Pinus pinaster resin was added into vegetable and mineral oil-based solvents in pure form with alkyd resin in different amounts and ink varnishes of different combinations were prepared. Then, printing inks were produced from these varnishes in pure and hybrid form. Following the assessment of the rheological properties of the inks prepared, printing tests were conducted to assess the printing quality parameters. Ideal mixing ratios of the natural resins in the ink were determined for printability. The environmental importance and advantages of the use of natural resins were discussed. Recommendations were given in line with the results to encourage widespread use of natural resins in near future. 相似文献
153.
Cecilia Arriagada Viviana A. Cavieres Charlotte Luchsinger Alexis E. Gonzlez Vanessa C. Muoz Jorge Cancino Patricia V. Burgos Gonzalo A. Mardones 《International journal of molecular sciences》2020,21(22)
Protein trafficking is altered when normal cells acquire a tumor phenotype. A key subcellular compartment in regulating protein trafficking is the Golgi apparatus, but its role in carcinogenesis is still not well defined. Golgi phosphoprotein 3 (GOLPH3), a peripheral membrane protein mostly localized at the trans-Golgi network, is overexpressed in several tumor types including glioblastoma multiforme (GBM), the most lethal primary brain tumor. Moreover, GOLPH3 is currently considered an oncoprotein, however its precise function in GBM is not fully understood. Here, we analyzed in T98G cells of GBM, which express high levels of epidermal growth factor receptor (EGFR), the effect of stable RNAi-mediated knockdown of GOLPH3. We found that silencing GOLPH3 caused a significant reduction in the proliferation of T98G cells and an unexpected increase in total EGFR levels, even at the cell surface, which was however less prone to ligand-induced autophosphorylation. Furthermore, silencing GOLPH3 decreased EGFR sialylation and fucosylation, which correlated with delayed ligand-induced EGFR downregulation and its accumulation at endo-lysosomal compartments. Finally, we found that EGF failed at promoting EGFR ubiquitylation when the levels of GOLPH3 were reduced. Altogether, our results show that GOLPH3 in T98G cells regulates the endocytic trafficking and activation of EGFR likely by affecting its extent of glycosylation and ubiquitylation. 相似文献
154.
Mauro D. Santos Ivonne Delgadillo Jorge A. Saraiva 《International Journal of Food Science & Technology》2020,55(3):1171-1179
Hyperbaric storage (HS) was evaluated as a new food preservation methodology at room temperature (RT) for beef and pork meat, both minced and in pieces, and compared to refrigeration (RF) storage. The meat samples were stored at 50, 75 and 100 MPa and variable RT up to 60 days. HS at 75 and 100 MPa could not only inhibit microbial growth but also inactivate microorganisms. Regarding physicochemical analyses, an overall equal to better pH maintenance in HS samples was achieved, and similar colour differences between HS and RF were observed. Generally, similarities in moisture content and drip loss between HS (mostly 75 and 100 MPa) and RF were detected (tendency for lower values in the former and higher values in the latter for the higher pressure level). Protein solubility revealed a decrease of sarcoplasmic protein values during storage with a pressure level dependency in some samples. 相似文献
155.
D. M. Mukhammadiev F. Kh. Ibragimov T. D. Mukhammadiev 《Journal of Machinery Manufacture and Reliability》2020,49(3):256-262
The dynamic characteristics of a saw gin as a subsystem with lumped and distributed parameters are considered in the paper. On the basis of investigation of the machine assembly, graphs are drawn that allow establishing the maximum values of the angle of relative rotation and the angle of rotation of the saw cylinder shaft under torsion. 相似文献
156.
C. G. Prosgolitis S. G. Lambrakos A. D. Zervaki 《Journal of Materials Engineering and Performance》2018,27(10):5102-5113
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size. 相似文献
157.
Buryakov A. M. Khusyainov D. I. Mishina E. D. Khabibullin R. A. Yachmenev A. E. Ponomarev D. S. 《Technical Physics Letters》2018,44(12):1115-1119
Technical Physics Letters - The influence of excitation photons energy on the relaxation times of photoexcited carriers is studied. The involved relaxation mechanisms are evaluated and the... 相似文献
158.
Dr. Emilianne M. Limbrick Audrey E. Yñigez-Gutierrez Callie C. Dulin Dagmara K. Derewacz Dr. Jeffrey M. Spraggins Dr. Kathryn M. McCulloch Prof. T. M. Iverson Prof. Brian O. Bachmann 《Chembiochem : a European journal of chemical biology》2020,21(23):3349-3358
Everninomicins are orthoester oligosaccharide antibiotics with potent activity against multidrug-resistant bacterial pathogens. Everninomicins act by disrupting ribosomal assembly in a distinct region in comparison to clinically prescribed drugs. We employed microporous intergeneric conjugation with Escherichia coli to manipulate Micromonospora for targeted gene-replacement studies of multiple putative methyltransferases across the octasaccharide scaffold of everninomicin effecting the A1, C, F, and H rings. Analyses of gene-replacement and genetic complementation mutants established the mutability of the everninomicin scaffold through the generation of 12 previously unreported analogues and, together with previous results, permitted assignment of the ten methyltransferases required for everninomicin biosynthesis. The in vitro activity of A1- and H-ring-modifying methyltransferases demonstrated the ability to catalyze late-stage modification of the scaffold on an A1-ring phenol and H-ring C-4’ hydroxy moiety. Together these results establish the potential of the everninomicin scaffold for modification through mutagenesis and in vitro modification of advanced biosynthetic intermediates. 相似文献
159.
160.
Fominski V. Yu. Nevolin V. N. Fominski D. V. Romanov R. I. Gritskevich M. D. 《Technical Physics Letters》2020,46(1):83-86
Technical Physics Letters - We present the results of a comparative investigation of the friction and wear characteristics of MoSx and MoSex coatings in an oxidizing medium (argon–air... 相似文献